Optical systems for multi-sensor endoscopes

ABSTRACT

There is provided herein an optical system for a tip section of a multi-sensor endoscope, the system comprising: a front-pointing camera sensor; a front objective lens system; a side-pointing camera sensor; and a side objective lens system, wherein at least one of said front and side objective lens systems comprises a front and a rear sub-systems separated by a stop diaphragm, said front sub-system comprises, in order from the object side, a first front negative lens and a second front positive lens, said rear sub-system comprises, in order from the object side, a first rear positive lens, an achromatic sub-assembly comprising a second rear positive lens and a third rear negative lens, wherein the following condition is satisfied: f(first rear positive lens)≤1.8f, where f is the composite focal length of the total lens system and f(first rear positive lens) is the focal length of said first rear positive lens.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.15/092,970, entitled “Optical Systems for Multi-Sensor Endoscopes” andfiled on Apr. 7, 2016, which is continuation of U.S. patent applicationSer. No. 13/882,004, of the same title and filed on May 23, 2013, whichis a national stage entry of PCT Application Number PCT/IL2011/000832,of the same title and filed on Oct. 27, 2011, which relies on U.S.Provisional Patent Application No. 61/407,495, of the same title andfiled on Oct. 28, 2010, for priority, all of which are herebyincorporated by reference in their entirety.

FIELD OF THE INVENTION

This invention relates to a wide FOV objective lens system for anendoscope.

BACKGROUND

Endoscopes have attained great acceptance within the medical community,since they provide a means for performing procedures with minimalpatient trauma, while enabling the physician to view the internalanatomy of the patient. Over the years, numerous endoscopes have beendeveloped and categorized according to specific applications, such ascystoscopy, colonoscopy, laparoscopy, upper GI endoscopy and others.Endoscopes may be inserted into the body's natural orifices or throughan incision in the skin.

An endoscope is usually an elongated tubular shaft, rigid or flexible,having a video camera or a fiber optic lens assembly at its distal end.The shaft is connected to a handle, which sometimes includes an ocularfor direct viewing. Viewing is also usually possible via an externalscreen. Various surgical tools may be inserted through a working channelin the endoscope for performing different surgical procedures.

There are known various endoscopes employing in their front insertionpart, optical heads for viewing the interior of a body cavity or lumensuch as the lower digestive track. Such optical head normally includesat least an illumination means for illuminating the object, an objectivelens system and a sensor array.

U.S. Pat. No. 6,956,703 discloses an objective lens for endoscopescomprises a front lens unit component and a rear lens unit component,between which a aperture stop is located, wherein the front lens unitcomponent comprises, in order from the object side, a first lens havinga negative refractive power, and a second lens having a positiverefractive power which directs a surface of the small radius ofcurvature toward the object side; wherein the rear lens unit componentcomprises a third lens having a positive refractive power which directsa surface of the small radius of curvature toward the image side, afourth lens having a positive refractive power, and a fifth lens havinga negative refractive power; and wherein the fourth lens and the fifthlens are cemented. The following condition is satisfied: 2.0<|f3/f|<3.0where f is the composite focal length of the total system and f 3 is thefocal length of the third lens. Still, the complexity of the objectsthat are inspected by the endoscope (for example, the asymmetric colonenvironment), requires high quality images capturing a wide Field ofView (FOV), which cannot be accomplished using only one detector.

More efforts have been undertaken to improve the optical design of thesesystems and to create a wide FOV, as seen for example, in U.S. Pat. No.5,870,234 entitled “Compact wide angle lens”, as well as U.S. Pat. No.6,476,851 entitled “Electronic endoscope”. Although these patents bringthe advantage of a wide FOV they mainly provide a front view. Anotherdisadvantage is a significant distortion in the periphery looking at theborders of the wide view image.

These disadvantages may be partially solved by using a multi image lensfor example as shown in US patent application number 2005/0168616entitled “Methods and apparatus for capturing images with a multi-imagelens” or by using other Omni-directional optical solutions, asdisclosed, for example, in U.S. Pat. No. 7,362,516 entitled “Opticallens providing Omni-directional coverage and illumination”. Thesetechnologies may support a wide FOV with relatively low distortion inthe periphery of the image however they suffer from a major disadvantageof low optical resolution on side views. Another disadvantage of thesetechnologies is the complexity and space consuming design whichtypically eliminates the possibility to combine other crucial featureslike jet, working channels and illuminating sources to the endoscope.

There is still a need in the art for endoscopes, such as colonoscopies,that provide a wide FOV, a wide range of Depth of Field/Depth of Focus(DOF) and acceptable resolution within the required dimensions of thedevice used of a medical application.

SUMMARY

The following embodiments and aspects thereof are described andillustrated in conjunction with systems, tools and methods which aremeant to be exemplary and illustrative, not limiting in scope.

It is an object of the current invention to provide optical system(s)for front looking and side looking cameras to be housed in the same head(tip) of an endoscope. The cameras together with their respective opticsystems are adapted to provide a high quality image capturing a wide FOVof the complex environment examined by the use of the endoscope.According to some embodiments, there is provided an endoscope comprisingat least a front looking camera and a side looking camera beingessentially perpendicular to one another. According to some embodimentsany of the cameras may include a small-sized image sensors such as CCDor CMOS sensors (hereinafter referred to as CCD but can also mean CMOSor any other sensor). In order to keep the outer diameter of the frontpart of the endoscope as small as possible, the optical systems used inthe plurality of cameras need to be compact. Specifically, the opticaltrack of the side looking camera needs to be short. In the case wheretwo side looking cameras are positioned along the same axis, preferablyessentially, perpendicular to the long axis of the endoscope, theminimal diameter of the endoscope's head is limited to at least twicethe total length of the cameras (which typically includes the opticaltrack of the camera, the sensor, and any electronic circuitry and wiringwhich may be located behind the sensor). Shortening the total lengthshould not affect the FOV or cause distortion. Both opticalcharacteristics should be maintained together with minimal total length.

Additionally, working channel(s) and fluid channel(s) need to traversethe endoscope's head. Thus, the diameter of the cameras and its opticalsystems needs to be small to allow for space occupied by the channels.Since different sensors may be used per field of view it opens theopportunity for additional working channels space giving big advantageto this application.

In order to effectively work within the confined space in a body cavity,the cameras may be equipped with wide-angle lens, capable of imagingclose objects and a wide range of working distances with preservation ofimage quality.

Optionally, several optical modules (cameras) in one endoscope head,with similar or different designs may be used, optionally each tuned toits desired Depth of Field (DOF).

According to some embodiments, there is provided herein an opticalsystem for a tip section of a multi-sensor endoscope, the systemcomprising: a front-pointing camera sensor; a front objective lenssystem; a side-pointing camera sensor; and a side objective lens system,wherein at least one of the front and side objective lens systemscomprises a front sub-system and a rear sub-system separated by a stopdiaphragm, wherein the front sub-system comprises, in order from theobject side, a first front negative lens and a second front positivelens, the rear sub-system comprises, in order from the object side, afirst rear positive lens, an achromatic sub-assembly comprising a secondrear positive lens and a third rear negative lens, wherein the followingcondition is satisfied:

f_((first rear positive lens))≤1.8f, where f is the composite focallength of the total lens system and f_((first rear positive lens)) isthe focal length of the first rear positive lens.

The front sub-system may further include an additional front positivelens (such as a meniscus lens) disposed between the first front negativelens and the second front positive lens (as seen, for example, in FIG. 4c ).

The rear sub-system may further include a rear protective glass situatedbetween the third rear negative lens and the front-pointing and/orside-pointing camera sensor, wherein the rear protective glass isadapted to protect a detector array of the front-pointing and/orside-pointing camera sensor.

According to some embodiments, the front-pointing camera sensor and thefront objective lens system may be adapted to provide a Depth of Focus(DOF) of between 4 and 110 mm. Optical system having a Depth of Focus(DOF) of between 4 and 110 mm may mean that the optical system isadapted to image objects at an object distance of 4-110 mm. Thefront-pointing camera sensor and the front objective lens system may beadapted to provide a Depth of Focus (DOF) of between 3.5 and 50 mm. Thefront-pointing camera sensor and the front objective lens system may beadapted to provide an effective spatial resolution of at least 60 linesper mm at Depth of Focus (DOF) of between 5 and 50 mm. Thefront-pointing camera sensor and the front objective lens system may beadapted to provide an effective angular resolution of about 2′ perdegree or less at Depth of Focus (DOF) of between 5 and 50 mm. Thefront-pointing camera sensor and the front objective lens system may beadapted to provide a Field of View (FOV) of at least 150 degrees. Thefront-pointing camera sensor and the front objective lens system may beadapted to provide a Field of View (FOV) of at least 170 degrees.

According to some embodiments, the front-pointing camera sensor and thefront objective lens system have a total optical length of 5 mm or less.

According to some embodiments, the side-pointing camera sensor and theside objective lens system may be adapted to provide a Depth of Focus(DOF) of between 3.5 and 50 mm. The side-pointing camera sensor and theside objective lens system may be adapted to provide an effectivespatial resolution of at least 60 lines per mm at Depth of Focus (DOF)of between 5 and 50 mm. The side-pointing camera sensor and the sideobjective lens system may be adapted to provide a Depth of Focus (DOF)of between 3 and 30 mm. The side-pointing camera sensor and the sideobjective lens system may be adapted to provide an effective angularresolution of about 2′ per degree or less at Depth of Focus (DOF) ofbetween 4.5 and 25 mm. The side-pointing camera sensor and the sideobjective lens system may be adapted to provide a Field of View (FOV) ofat least 150 degrees. The side-pointing camera sensor and the sideobjective lens system may be adapted to provide a Field of View (FOV) ofat least 170 degrees.

According to some embodiments, the side-pointing camera sensor and theside objective lens system may have a total optical length of 5 mm orless (for example, 4 mm or less, 3 mm or less).

According to some embodiments, the diameter of the first front negativelens may be 2.5 mm or less (without the barrel or lens holder).

According to some embodiments, there is provided an objective lenssystem for at least one of a front-pointing camera sensor and aside-pointing camera sensor of a multi-sensor endoscope, the objectivelens system comprising: a front sub-system and a rear sub-systemseparated by a stop diaphragm, wherein the front sub-system comprises afirst front negative lens and a second front positive lens, and the rearsub-system comprises a first rear positive lens, an achromaticsub-assembly comprising a second rear positive lens and a third rearnegative lens, wherein the following condition is satisfied:

f_((first rear positive tens))≤1.8f, where f is the composite focallength of the total lens system and f(first rear positive lens) is thefocal length of the first rear positive lens.

According to some embodiments, there is provided a tip section of amulti-sensor endoscope comprising an optical system comprising: afront-pointing camera sensor; a front objective lens system; aside-pointing camera sensor; and a side objective lens system, whereinat least one of the front and side objective lens systems comprises afront sub-system and a rear sub-system separated by a stop diaphragm,the front sub-system comprises a first front negative lens and a secondfront positive lens, the rear sub-system comprises a first rear positivelens, an achromatic sub-assembly comprising a second rear positive lensand a third rear negative lens, wherein the following conditions aresatisfied:

f_((first rear positive lens))≤1.8f, where f is the composite focallength of the total lens system and f_((first rear positive lens)) isthe focal length of the first rear positive lens.

More details and features of the current invention and its embodimentsmay be found in the description and the attached drawings.

Unless otherwise defined, all technical and scientific terms used hereinhave the same meaning as commonly understood by one of ordinary skill inthe art to which this invention belongs. Although methods and materialssimilar or equivalent to those described herein can be used in thepractice or testing of the present invention, suitable methods andmaterials are described below. In case of conflict, the patentspecification, including definitions, will control. In addition, thematerials, methods, and examples are illustrative only and not intendedto be limiting.

BRIEF DESCRIPTION OF THE DRAWINGS

Some embodiments of the invention are herein described, by way ofexample only, with reference to the accompanying drawings. With specificreference now to the drawings in detail, it is stressed that theparticulars shown are by way of example and for purposes of illustrativediscussion of the preferred embodiments of the present invention only,and are presented in the cause of providing what is believed to be themost useful and readily understood description of the principles andconceptual aspects of the invention. In this regard, no attempt is madeto show structural details of the invention in more detail than isnecessary for a fundamental understanding of the invention, thedescription taken with the drawings making apparent to those skilled inthe art how the several forms of the invention may be embodied inpractice.

In order to understand the invention and to see how it may be carriedout in practice, embodiments will now be described, by way ofnon-limiting example only, with reference to the accompanying drawings,in which:

FIG. 1 a schematically depicts an external isometric view of anendoscope having multiple fields of view according to an exemplaryembodiment of the current invention.

FIG. 1 b schematically depicts a front view of an endoscope havingmultiple fields of view according to an exemplary embodiment of thecurrent invention.

FIG. 1 c schematically depicts a side view of endoscope having multiplefields of view according to an exemplary embodiment of the currentinvention.

FIG. 2 a schematically depicts a cross section of an endoscope havingmultiple fields of view, for use within bodily cavity according to anexemplary embodiment of the current invention.

FIG. 2 b schematically depicts a cross section of an endoscope fronthead having multiple fields of view showing some details of the headaccording to an exemplary embodiment of the current invention.

FIG. 2 c schematically depicts a cutout isometric view of an endoscopehaving multiple fields of view according to another exemplary embodimentof the current invention.

FIG. 2 d schematically depicts another cutout isometric view of anendoscope having multiple fields of view according to an exemplaryembodiment of the current invention.

FIG. 3 schematically depicts a cross section of a lens assembly of acamera head, according to an exemplary embodiment of the currentinvention.

FIG. 4 a schematically illustrates example of light propagation withinan objective lens systems according to an exemplary embodiment of thecurrent invention.

FIG. 4 b schematically illustrates another example of light propagationwithin an objective lens system according to an exemplary embodiment ofthe current invention.

FIG. 4 c schematically illustrates another example of light propagationwithin an objective lens system according to an exemplary embodiment ofthe current invention.

DETAILED DESCRIPTION

Before explaining at least one embodiment of the invention in detail, itis to be understood that the invention is not necessarily limited in itsapplication to the details set forth in the following description orexemplified by the Examples. The invention is capable of otherembodiments or of being practiced or carried out in various ways.

The terms “comprises”, “comprising”, “includes”, “including”, and“having” together with their conjugates mean “including but not limitedto”.

The term “consisting of” has the same meaning as “including and limitedto”.

The term “consisting essentially of” means that the composition, methodor structure may include additional ingredients, steps and/or parts, butonly if the additional ingredients, steps and/or parts do not materiallyalter the basic and novel characteristics of the claimed composition,method or structure.

As used herein, the singular form “a”, “an” and “the” include pluralreferences unless the context clearly dictates otherwise. For example,the term “a compound” or “at least one compound” may include a pluralityof compounds, including mixtures thereof.

Throughout this application, various embodiments of this invention maybe presented in a range format. It should be understood that thedescription in range format is merely for convenience and brevity andshould not be construed as an inflexible limitation on the scope of theinvention. Accordingly, the description of a range should be consideredto have specifically disclosed all the possible sub-ranges as well asindividual numerical values within that range.

It is appreciated that certain features of the invention, which are, forclarity, described in the context of separate embodiments, may also beprovided in combination in a single embodiment. Conversely, variousfeatures of the invention, which are, for brevity, described in thecontext of a single embodiment, may also be provided separately or inany suitable sub-combination or as suitable in any other describedembodiment of the invention. Certain features described in the contextof various embodiments are not to be considered essential features ofthose embodiments, unless the embodiment is inoperative without thoseelements.

In discussion of the various figures described herein below, likenumbers refer to like parts. In some cases, pluralities of similar oridentical elements are marked with same numbers followed by letters, insome cases; same number without the letter refers to any of theseelements. The drawings are generally not to scale. For clarity,non-essential elements were omitted from some of the drawing.

The optical setup for endoscopes typically used in the prior artrequires a relatively large overall optical length (total optical track)of the entire optical system, which is disadvantageous for endoscopes,in particular those used as colonoscopes and gastroscopes, particularlyif used in endoscopes having side-viewing camera or cameras, such asendoscopes according to embodiments of the present invention.

In addition, in sensors (such as CCD sensors) used in endoscopes of theprior art, the pixels are partially covered by a photo-shielding film,so that the light energy is concentrated in the center of the pixel,where there is a “window” in the photo-shielding film. This improves thesignal-to-noise ratio and increases the light utilization efficiency.However, this also causes the sensor to be sensitive to incident anglesbetween the light rays which have passed the micro-lenses of the sensorand the optical axis of the system. Thus, light rays having relativelysmall incident angles may reach the pixel, while light rays havingrelatively large incident angles (between the light rays which havepassed the micro-lenses of the sensor and the optical axis of thesystem) may not reach the “window” and thus the pixel, leading tosignificant energy losses. The losses are maximized at the edges of thefield of view, i.e. for light rays having incident angles close to thatof the chief ray.

There is thus provided herein, according to some embodiments, a lenssystem (assembly) configured for use in an endoscope, such ascolonoscope, particularly for use in a multi-sensorendoscope/colonoscope. The lens system, (optionally together with thesensor) according to some embodiments of the invention, has a shorttotal optical length (track), for example, 5 mm or less. The lenssystem, according to some embodiments of the invention, is configured toprovide a large incident angle, for example, a chief incident angle (forexample the incident angles forming by rays R₆ in FIGS. 4 a-4 c ) largerthan 20°, larger than 25°, larger than 30° or between about 20-40°. Thelens system, according to some embodiments of the invention providesminimal distortion (for example, less than 80%).

According to some embodiments, the sensor which is used together withthe lens system, is configured to have a window in the photo-shieldingfilm configured to allow rays having large incident angle (for example,a chief incident angle larger than 20°, larger than 25°, larger than 30°or between about 20-40°) to reach the pixel and thus improve thedistortion. According to some embodiments, the width of the window (orany other dimensional parameter) may be about 30-60% of the width of thecorresponding pixel. According to some embodiments, the micro-lenses ofthe sensor may be configured to provide substantially aplanaticconditions. In other words, the sensor may be configured to provide animage substantially free of aberrations.

FIG. 1 a schematically depicts an external isometric view of anendoscope (for example, a colonoscope) 200 having multiple fields ofview according to an exemplary embodiment of the current invention.

According to an exemplary embodiment of the current invention, head 230of endoscope 200 comprises at least a forwards looking camera (such as aTV camera) and at least one side looking camera (such as a TV camera).

FIG. 1 a shows front camera element 236 of forwards looking camera 116(seen in FIG. 2 c ) on the front face 320 of head 230. The term “cameraelement” may generally refer to a camera and the optical system/assemblyrelated to the camera. Optical axis of forwards looking camera 116 (seenfor example in FIG. 2 a ) is substantially directed along the longdimension of the endoscope. However, since forwards looking camera 116is typically a wide angle camera, its Field of View (FOV) may includeviewing directions at large angles to its optical axis. Additionally,optical windows 242 a and 242 b of discrete light sources such as LightEmitting Diodes (LEDs) 240 a and 240 b are also seen on front face 320of head 230. It should be noted that number of LEDs used forillumination of the FOV may vary. Distal opening 340 of working channel262 (seen for example in FIG. 2 d ) may preferably be located on frontface 320 of head 230, such that a surgical tool inserted through workingchannel 262 and deployed beyond front face 320 may be viewed by forwardslooking camera 116.

Distal opening 344 of a fluid channel may preferably also be located onfront face 320 of head 230. The fluid channel leading to distal opening344 may be used as a jet channel for cleaning the colon.

Liquid injector 346 having a nozzle 348 aimed at front camera element236 is used for injecting fluid to wash contaminants such as blood,feces and other debris from front camera element 236 of forwards lookingcamera. Optionally the same injector is used for cleaning both frontcamera element 236 and one or both optical windows 242 a and 242 b.Injector 346 may receive fluid (for example, water and/or gas) from thefluid channel or may be fed by a dedicated cleaning fluid channel.

Visible on the side wall 362 of head 230 is the front camera element 256of side looking camera 220 (two such cameras are seen in FIG. 2 a ) andoptical window 252 of a discrete light sources such as LED 250. It isnoted that the number of the discrete light sources may vary. Opticalaxis of side looking camera 220 may be substantially directedperpendicular to the long dimension of the endoscope. However, sinceside looking camera 220 is typically a wide angle camera, its field ofview may include viewing directions at large angles to its optical axis.

Liquid injector 366 having a nozzle 368 aimed at front looking cameraelement 256 is used for injecting fluid to wash contaminants such asblood, feces and other debris from front camera element 256 of sidelooking camera. Optionally the same injector is used for cleaning bothfront camera element 256 and optical windows 252. Preferably, injectors346 and 366 are fed from same channel. An optional groove 370 helpsdirecting the cleaning fluid from nozzle 368 towards front cameraelement 256. Groove 370 may be beneficial when side wall 362 is near orpressed against the rectal wall. Optionally, injector 366 may be atleast partially recessed in groove 370, thus reducing the maximumdiameter of head 230 and reduce the risk of injury to the rectal walldue to friction with injector 366.

In the depicted embodiment, flexible shaft 260 is constructed of aplurality of links 382 connected to each other by pivots 384. Links 382allows pushing, pulling and rotating the endoscope while pivots 384provide limited flexibility. The shaft is preferably covered with anelastic sheath (removed for clarity in this figure). The lumen in links382 holds the working channel 262. Not seen in this figure are the fluidchannel connected to opening 344, optional cleaning fluid channel andelectrical cables supplying power to the LEDs and cameras andtransmitting video signals from the camera. Generally, the shaft mayalso comprise mechanical actuators (not seen), for example cablesattached to the links for directing and aiming the head during use.

It should be noted that while only one side looking camera is seen inFIG. 1 a , optionally, according to some embodiments, two or more sidelooking cameras may be located within head 230. When two side lookingcameras are used, the side looking cameras are preferably installed suchthat their field of views are substantially opposing. According to someembodiments, Different configurations and number of side looking camerasare possible and covered within the general scope of the currentinvention.

FIG. 1 b schematically depicts a front view of head 230 of endoscope 200having multiple fields of view according to an exemplary embodiment ofthe current invention.

According to an exemplary embodiment of the current invention, head 230of endoscope 200 comprises at least a forwards looking camera and atleast one side looking camera. FIG. 2 b shows a front camera element 236of forwards looking camera 116 on the front face 320 of head 230.Additionally, optical windows 242 a and 242 b of LEDs 240 a and 240 bare also seen on front face 320 of head 230. Distal opening 340 ofworking channel and distal opening 344 of a fluid channel are preferablyalso located on front face 320 of head 230. Liquid injector 346 having anozzle 348 is also visible in this view.

Additionally, Liquid injectors 366 a and 366 b aimed at side lookingcamera element 256 a and 256 b respectively are used for injecting fluidto wash contaminants such as blood, feces and other debris from frontcamera element 256 of side looking cameras.

FIG. 1 c schematically depicts a side view of endoscope 200 havingmultiple fields of view according to an exemplary embodiment of thecurrent invention.

FIG. 1 c shows front camera element 256 of side looking camera 220,groove 370 and optical window 252 on the side wall 362 of head 230.Liquid injectors 346 and 366 are also visible in this view.

FIG. 2 a schematically depicts a cutout isometric view of an endoscope400 having multiple fields of view according to another exemplaryembodiment of the current invention.

According to an exemplary embodiment of the current invention, head 230of endoscope 200 comprises at least a forwards looking camera 116 andtwo side looking cameras 220 a and 220 b.

Optical windows 242 a and 242 b of LEDs used for forward illuminationare also seen on front face of head 230.

Distal opening 340 of working channel is preferably located on frontface of head 230 such that a surgical tool inserted through the workingchannel 262 and deployed beyond front face may be viewed by forwardslooking camera 116.

Distal opening 344 of a fluid channel is preferably also located onfront face of head 230. The fluid channel leading to distal opening 344may be used as a jet channel for cleaning the colon.

Liquid injector 346 having a nozzle aimed at front camera element ofcamera 116 is used for injecting fluid to wash contaminants such asblood, feces and other debris from front camera element of forwardslooking camera 116. Optionally the same injector is used for cleaningthe front camera element and one or both optical windows 242 a and 242b. Injector 346 may receive fluid from the fluid channel or may be fedby a dedicated cleaning fluid channel.

Visible on right hand side of head 230 is the front camera element 256 bof side looking camera 220 b and optical window 252 b of sideilluminating LED.

Liquid injector 366 b having a nozzle aimed at front camera element 256b is used for injecting fluid to wash contaminants such as blood, fecesand other debris from front camera element 256 b of side looking camera220 b. Optionally the same injector is used for cleaning both frontcamera element 256 b and optical windows 252 b. An optional groove 370 bhelps directing the cleaning jet from injector 366 b towards frontcamera element 256 b.

Although not seen in this figure, it is understood that equivalentelements 366 a, 370 a, 256 a and 252 a are present on the left hand sideof head 230.

Preferably, all the injectors 346 and 366 are fed from same channel.

In the depicted embodiment, flexible shaft 260 is constructed of aplurality of links 382 (only one is marked for clarity). Electricalcable 396 within shaft 260 is seen connected to cameras 116, 220 a and220 b. The same or separate electrical cable is used to power the LEDs.

FIG. 2 b schematically depicts a cross section of an endoscope 200having multiple fields of view showing some details of the head 230according to an exemplary embodiment of the current invention.

According to the current invention, head 230 of endoscope 200 comprisesat least a forwards looking camera 116 and two side looking cameras 220a and 220 b. Each of cameras 116 and 220 is provided with an opticalimaging system such as lens assemblies (systems) 132 and 232respectively and solid state detector arrays 134 and 234 respectively.Front camera elements 236 and 256 of cameras 116 and 220 respectivelymay be a flat protective window, but optionally an optical element usedas part of the imaging systems such as solid state detector arrays 134and 234 respectively. Optionally, cameras 116 and 220 are similar oridentical, however different camera designs may be used, for example,field of views 118 and 218 may be different. Additionally oralternatively, other camera parameters such as: resolution, lightsensitivity, pixel size and pixel number, focal length, focal distanceand depth of field may be selected to be same or different.

Light is provided by Light Emitting Diodes (LED) that illuminates thefield of views. According to some embodiments, white light LEDs may beused. According to other embodiments, other colors of LEDs or anycombination of LEDs may be used (for example, red, green, blue,infrared, ultraviolet).

In the depicted embodiment, field of view 118 of forwards looking camera116 is illuminated by two LEDs 240 a and 240 b located within theendoscope head 230 and protected by optical window 242 a and 242 brespectively.

Similarly, in the depicted embodiment, field of views of side lookingcamera 220 is illuminated by a single LED 250 located within theendoscope head 230 and protected by optical window 252. It should benoted that number of LED light sources and their position in respect tothe cameras may vary within the scope of the current invention. Forexample few LEDs may be positioned behind the same protective window, acamera and an LED or plurality of LED may be located behind the sameprotective window, etc.

Head 230 of endoscope 200 is located at the distal end of a flexibleshaft 260. Similarly to shafts of the art, shaft 260 comprises a workingchannel 262 for insertion of surgical tools. Additionally, shaft 260 maycomprises channels for irrigation, insufflation, suction and supplyingliquid for washing the colon wall.

FIG. 2 c schematically depicts a cross section cutout of an endoscope200 showing some details of the head 230 according to an exemplaryembodiment of the current invention. For simplicity, details of one ofthe two side looking cameras are marked in the figure.

According to the current invention, head 230 of endoscope 200 comprisesat least one side looking camera 220. Each of cameras 220 is providedwith an optical imaging system such as lens assemblies 232 and solidstate detector arrays 234. Front camera element 256 of camera 220 may bea flat protective window or an optical element used as part of theimaging system 232.

FIG. 2 d schematically depicts a cross section of an endoscope 200having multiple fields of view showing some details of the head 230according to an exemplary embodiment of the current invention.

According to some embodiments of the current invention, the interior ofthe head 230 comprises forward looking and side looking cameras 116 and220, respectively. Cameras 116 and/or 220 comprise lens assemblies 132and 232 (not shown), respectively, having a plurality of lenses 430 to434 and protective glass 436 (not shown) and a solid state detectorarrays 134 and 234 (not shown) connected to a printed circuit board 135and 235 (not shown) respectively. It is noted that cameras 116 and 220or any element related to them (such as lens assemblies 132 and 232,lenses 430 to 434 and protective glass 436, solid state detector arrays134 and 234 and/or printed circuit board 135 and 235) may be the same ordifferent. In other words the front looking camera and the side lookingcamera(s) may be the same or different in any one or any combinations oftheir components or other element related to them (such as opticalelements).

FIG. 3 schematically depicts a cross section of cameras 116 or 220,showing some details of lens assemblies 132 and 232 according to anexemplary embodiment of the current invention. It should be noted thataccording to some embodiments of the invention, cameras 116 and 220 maybe similar or different. Optionally, the focusing distance of camera 116is slightly different than that of camera 220. Differences in focusingdistances may be achieved, for example, by (slightly) changing thedistance between the lenses that comprise the lens assemblies 132 and/or232, or between the lens assembly and the detector array.

Air gap “S” between lenses 431 and 432 acts as a stop. Air gap S mayaffect the focal range (the distance between the closest object andfarther objects that can be imaged without excessive blurring caused bybeing out of optimal focusing of the lens system).

According to an exemplary embodiment of the current invention, cameras116 and 220 comprise lens assemblies 132 and 232 respectively. The lensassemblies comprise a set of lenses 430 to 434 and protective glass 436.

Lenses 430 to 434 are situated within a (optionally metallic) barrel 410and connector thereto (for example, glued in barrel 410). Any one oflens assemblies 132 and/or 232 may also include an adapter 411,optionally, as shown in FIG. 3 , positioned within barrel 410. Adapter411 is configured to adjust the location of one or more of the lensesand adjust the distance between lenses. Adapter 411 may also beconfigured to function as a stop (in this case, between lenses 432 and433. Protective glass 436 is situated in proximity to the solid statedetector arrays 134 or 234 and is optionally attached thereto.

Focal distance (the distance to the object to be optimally focused bythe lens system) may be changed by changing the distance between lenses434 and protective glass 436. As lens 434 is fixed to the barrel, andprotective glass 436 is fixed to lens holder 136 (236), this distancemay be varied by changing the relative positioning of lens holder 136(236) with respect to barrel 410. The space between the lenses 434 andprotective glass 436 may be an empty space or may be filled with glassor other transparent material, or a tubular spacer may be inserted toguarantee the correct distance between these lenses. Optionally, opticalfilters may be placed within the space. Cameras 116 and 220 furthercomprise solid state detector arrays 134 and 234 respectively. Solidstate detector arrays 134 and 234 may each be connected to printedcircuit boards. An electrical cabling may connect the printed boards toa central control system unit of the endoscope.

Solid state detector arrays 134 and 234 are attached to lens holders 136and 236 respectively. Lens holder 136 or 236 are attached to lensassemblies 132 or 232 respectively by attaching detector array cover tobarrel 410.

In some applications, protective glass 436 may be a flat-flat opticalelement, acting primarily as a protection of the detector array (such asdetector arrays 134 and 234), and may optionally be supplied with thearray. However, optical properties of protective glass 436 need to beaccounted for in the optical design.

In order to assemble lens assemblies 132 or 232, lens 430 may first beinserted from left, then 431, and 432 from right. Lenses 433 and 434which may be glued together (or separated for example by air) are theninserted from right. The complete set is now assembled in a barrel. Theassembled detector (such as detector arrays 134 and 234), protectiveglass 436 and cover 136(236) are then added.

FIGS. 4 a, 4 b and 4 c illustrate three examples for the lens assembliessuch as lens assemblies 132 and 232 according to the present invention,having objective lens systems 510, 520 and 530 respectively. The sensorused in the lens assemblies 132 and 232, according to this exemplaryembodiment, may be a Charge Coupled Device sensor (CCD) having an arrayof micro-lenses but other sensors, such as CMOS, may also be used.

In an exemplary embodiment of the invention, a color CCD camera havingresolution of approximately 800×600 pixels were used with total activearea of approximately 3.3×2.95 mm. The optical resolution of the lens,according to exemplary embodiments of the current invention, wasdesigned to match the resolution of the sensor. The objective lenssystem 510 (520/530) are preferably corrected for chromatic; sphericaland astigmatism aberrations. In an exemplary embodiment of theinvention, objective lens system 510 (520/530) is approximately 4.60 mm(4.62) total length, measured from front face of front lens to the frontsurface of the sensor. In an exemplary embodiment of the invention,objective lens systems 510 and 520 are wide angle objectives havingapproximately 170 degrees acceptance angle. In an exemplary embodimentof the invention, objective lens system 510 (520/530) has a short focaldistance of measured from the front surface of the front lens to theimaged object. In an exemplary embodiment of the invention objectivelens system 510 (520/530) has Depth of Focus (DOF) allowing toeffectively image objects between 4-110 mm (or between, 3.5-50 mm). Inan exemplary embodiment of the invention, objective lens system 510, 520and 530 has maximum diameter of about 2.5 mm, defined by the diameter ofthe front lens, and is housed in a barrel having maximum outer diameterof approximately 3.6 mm. It should be noted that other design parametersmay be selected within the general scope of the current invention.

The objective lens system 510 (520/530) has an optical axis “0” depictedby the dashed line. The lens system comprises a front sub-system 510 a(520 a/530 a) and a rear sub-system 510 b (520 b/530 b).

Front sub-system 510 a (520 a) (FIG. 4 a (4 b)) comprises a front lens430 (430′) located closest to the object to be viewed, having a negativepower and lens 431(431′) having a positive power.

Front lens 430 (430′) is oriented with its concave surface facing towardthe optical image formed and away from the object to be viewed andoptionally having a diameter substantially greater than the largestdimension of the rear sub-system 510 b in the direction perpendicular tothe optical axis. Lens 431(431′) has a positive power.

Rear sub-system 510 b (520 b) comprises lenses 432, 433; 434; andprotective glass 436 (lenses 432′; 433′; 434′; and 436′), wherein 432(432′), has a positive power, 433 (433′) has a positive power, 434(434′) has a negative power, and 436 (436′) has essentially no opticpower. It is noted that protective glass 436 (436′) may be a part of thesensor or a part of the rear sub-system 510 b (520 b). Lenses 433 and434 (433′ and 434′) of the rear sub-system 510 b (520 b) compose anachromatic sub-assembly (a compound achromatic sub-assembly as seen inFIG. 4 a , where lenses 433 and 434 are cemented or non-compoundachromatic sub-assembly as seen in FIG. 4 b , where lens 433′ and lens434′ are separated). Lens 433 (433′) may be biconvex with radius ofcurvature of its front surface being smaller than radius of curvature ofits rear surface, as indicated in Tables T₁, T₂ below.

Lens 432 of the objective lens systems 510 may have a focal length f₄₃₂satisfying the following condition: f₄₃₂≤1.8f, where f is the compositefocal length of the total system. Particularly, for the data indicatedin Table T₁ f₄₃₂=2.05 and f=1.234 mm, the condition: f₄₃₂≤1.8f issatisfied.

Lens 432′ of the objective lens systems 520 may have a focal lengthf_(432′) satisfying the following condition: f₄₃₂≤1.8f.

Particularly, for the data indicated in Table T₂ f₄₃₂=2.05 and f=1.15mm, the condition: f₄₃₂≤1.8f is satisfied.

The lenses may be coated with an anti-reflection coating (AR coating)for further improving the efficiency of the lens assemblies 132 (232).

An effective aperture stop S₁ (S₂) is formed between lenses 431 and 432(431′ and 432′). Effective aperture stop S₁ (S₂) may separate betweenfront sub-system 510 a (520 a) and rear sub-system 510 b (520 b).

Front sub-system 530 a (FIG. 4 c ) comprises a front lens 430″ locatedclosest to the object to be viewed, having a negative power and lens431″, having a positive power. Front sub-system 530 a (FIG. 4 c )further comprises an additional front positive lens (such as themeniscus lens 429) disposed between the first front negative lens 430″and the second front positive lens 431″.

Front lens 430″ is oriented with its concave surface facing toward theoptical image formed and away from the object to be viewed andoptionally having a diameter substantially greater than the largestdimension of the rear sub-system 530 b in the direction perpendicular tothe optical axis.

Rear sub-system 530 b comprises lenses 432″, 433″, 434″; and protectiveglass 436″, wherein 432″, has a positive power, 433″ has a positivepower, 434″ has a negative power, and 436″ has essentially no opticpower. It is noted that protective glass 436″ may be a part of thesensor or a part of the rear sub-system 530 b. Lenses 433″ and 434″compose an achromatic sub-assembly of the rear sub-system 530 b and mayor may not be cemented to each other. Lens 433″ may be biconvex withradius of curvature of its front surface being smaller than radius ofcurvature of its rear surface, as indicated in Table T₃ below.

Lens 432″ of the objective lens systems 530 may have a focal length f₄₃₂satisfying the following condition: f_(432″)≤1.8f, where f is thecomposite focal length of the total system. Particularly, for the dataindicated in Table T₃ f_(432″)=2.26 and f=1.06 mm, the condition:f_(432″)≤1.8f is satisfied.

The lenses may be coated with an anti-reflection coating (AR coating)for further improving the efficiency of the lens assemblies 132 (232).

An effective aperture stop S₃ is formed between lenses 431″ and 432″.Effective aperture stop S₃ may separate between front sub-system 530 aand rear sub-system 530 b.

Tables T₁ T₂ and T₃ summarize the parameters of lenses in the objectivelens systems 510, 520 and 530, respectively, according to someembodiments of the current invention:

TABLE T₁ (FOV = 164°, DOF = 3-110 mm. f = 1.234 mm, total optical track4.09 mm) Semi-Diameter Semi-Diameter Lens Type R₁ R₂ Th D Glass d₁/2d₂/2 f_(mm) 430 Negative 15 0.7 0.2 0.18 N-LASF3 1.2 0.64 −0.837 431Plano-convex 0.9 Infinity 0.56 0.27 N-LASF3 0.8 0.8 1.02 S₁ Stop 0.050.104 432 Plano-convex Infinity −1.0 0.75 0.09 FK5 0.8 0.8 2.05 433Biconvex 1.93 −4.2 0.75 0.005 N-LAK22 1.1 1.1 2.13 434 Biconcave −4.24.44 0.3 0.65 N-SF66 1.1 1.2 −2.3 436 Protection Glass Infinity Infinity0.3 0 N-BK7 1.5 1.5 Infinity

TABLE T₂ (FOV = 164°, DOF = 3-110 mm, f = 1.15 mm, total optical track4.09 mm) Semi-Diameter Semi-Diameter Lens Type R₁ R₂ Th D Glass d₁/2d₂/2 f_(mm) 430 Negative 6 0.7 0.2 0.3 N-LASF3 1.2 0.66 −0.91 431Plano-convex 1.26 Infinity 0.50 0.27 N-LASF3 0.8 0.8 1.43 S₁ Stop 0.050.105 432 Plano-convex Infinity −1.0 0.60 0.15 FK5 0.8 0.8 2.05 433Biconvex 1.67 −1.65 0.70 0.30 FK5 0.95 0.95 1.83 434 Meniscus −1.33−12.0 0.35 0.40 N-SF66 1.0 1.2 −1.65 436 Protection Glass InfinityInfinity 0.3 0 N-BK7 1.5 1.5 Infiniy

Table 3, shows an example of a six-component system also comprising anadditional positive lens 429 (for example, as indicated in Table 3, ameniscus lens).

TABLE T₃ (FOV = 164°, DOF = 3-110 mm, f = 1.06 mm, total optical track4.69 mm) Semi-Diameter Semi-Diameter Lens Type R₁ R₂ Th D Glass d₁/2d₂/2 f_(mm) 430″ Negative 4.3 0.75 0.2 0.22 N-LASF3 1.3 0.72 −1.06 429Meniscus 0.95 0.9 0.44 0.18 N-SF66 0.8 0.65 5.75 431″ Plano-convex 2.0Infinity 0.75 0.02 N-LASF3 0.8 0.8 2.26 S₃ Stop 0.02 0.116 432″Plano-convex Infinity −1.0 0.78 0 N-PSK57 0.8 0.8 1.69 433″ Biconvex2.52 −2.0 0.50 0.154 YGH52 0.8 0.8 1.49 434″ Biconcav −1.44 11.0 0.250.91 PBH56 0.8 0.9 −1.50 436″ Protection Glass Infinity Infinity 0.3 0N-BK7 1.5 1.5 InfiniyR₁—radius of curvature of the lens front surface (front surface is thesurface facing the direction of the object);R₂—radius of curvature of the lens rear surface (facing away from theobject);Th—thickness of the lens—from center of front surface to center of rearsurface;Glass—lens glass type;d₁—radius of the front optical surface of the lens;d₂—radius of the rear optical surface of the lens;D—distance between components such as lenses, measured front center ofrear surface of the component, such as lens to the front surface of thenext optical element (in the case of a stop, S, the distance is measuredfront center of rear surface of a component on the front side of thestop, to the front surface of the next component),As commonly used, radius of curvature equal to infinity is interpretedas planar. All lenses are optionally spherical.

FIGS. 4 a, 4 b and 4 c also show the propagation of five incident raysof light R₁ to R₆ through the objective lens system 510, 520 and 530respectively, from the front lens 430 (FIG. 4 a ), 430′ (FIG. 4 b ) or430″ (FIG. 4 c ) till the creating of an image of the object at an imageplane.

Rays R₁ to R₆, enter the lens assembly at angles α₁ (alpha 1) to a₆(alpha 6), respectively, for example, essentially equal to the followingangles: a₁=0°, a₂=45°, a₃=60°, a₄=75° and a₅=84°. The correspondingincident angles (the angles between the light rays which have passed themicro-lenses of the sensor and the optical axis of the system) are □₁(beta 1)-□₆ (beta 6). According to some embodiments, the chief incidentangle (for example the incident angles forming by rays R₆ in FIGS. 4 a-4c ) is larger than 20°, larger than 25°, larger than 30° or betweenabout 20-40°. The lens system, according to some embodiments of theinvention provides minimal distortion (for example, less than 80%).

The optical system assembly 132 (232) may be assembled by a methodcomprising the step of:

Optionally, cementing the rear doublet of lenses 433-434 (433′-434′);

and:

Assembling in the barrel the front lenses 430 (430′);

Assembling lens 431 (431′) in the barrel;

Assembling lens 432 (432′) in the barrel;

Assembling in the barrel, the rear doublet 433-434 (433′-434′); and

Note that front lens 430 (430′) may be assembled last.

Although the invention has been described in conjunction with specificembodiments thereof, it is evident that many alternatives, modificationsand variations will be apparent to those skilled in the art.Accordingly, it is intended to embrace all such alternatives,modifications and variations that fall within the spirit and broad scopeof the appended claims. All publications, patents and patentapplications mentioned in this specification are herein incorporated intheir entirety by reference into the specification, to the same extentas if each individual publication, patent or patent application wasspecifically and individually indicated to be incorporated herein byreference. In addition, citation or identification of any reference inthis application shall not be construed as an admission that suchreference is available as prior art to the present invention.

We claim:
 1. An objective lens system comprising: a plurality of lenses;a first sleeve having a first passage extending therethrough; an imagesensor received in the first passage; and a second sleeve received inthe first passage, wherein the second sleeve has a second passageextending therethrough, wherein the plurality of lenses are received inthe second passage, and wherein the second sleeve is configured to movelongitudinally within the first sleeve, without rotating about a centrallongitudinal axis of the first passage, to change a distance between:(a) a lens of the plurality of lenses that is closest to the imagesensor, and (b) the image sensor; wherein the plurality of lensesinclude a first group of lenses, wherein the first group of lensesincludes: a first negative lens, a first positive lens positioned on animage side of the negative lens, and a front meniscus lens disposedbetween the negative lens and the positive lens; and wherein theplurality of lenses further includes a second group of lenses separatefrom the first group of lenses, wherein the second group of lensesincludes: a second positive lens, and an achromatic sub-assemblycomprising: a third positive lens, and a second negative lens, whereinthe achromatic sub-assembly is positioned on an image side of the secondpositive lens.
 2. The objective lens system of claim 1, wherein theobjective lens system has a length of 5 mm or less.
 3. The objectivelens system of claim 1, wherein the image sensor is directly coupled tothe lens holder.
 4. The objective lens system of claim 1, wherein atleast two lenses of the second plurality of lenses are positioned withinthe lens holder.
 5. The objective lens system of claim 1, furthercomprising a protective cover, the protective cover comprising a pane ofprotective glass between the plurality of lenses and the image sensor.6. The objective lens system of claim 5, wherein the pane of protectiveglass is directly coupled to the lens holder.
 7. The objective lenssystem of claim 1, wherein the image sensor is directly coupled to aproximalmost end of the lens holder.
 8. The objective lens system ofclaim 1, wherein a distalmost lens of the plurality of lenses protrudesdistally from the lens barrel.
 9. The objective lens system of claim 1,wherein the first passage is defined by a radially-inward facing surfaceof the lens holder.
 10. The objective lens system of claim 1, whereinthe first passage extends from a proximal end of the lens holder to adistal end of the lens holder.